The invention relates to postage meters and more particularly to electronic postage meters of the type having a microprocessor for controlling the printing of value and accounting for such printing.
Devices of this type are generally known, and are discussed, for example in U.S. Pat. No. 3,978,457. This patent discloses a system for a postal meter which includes a keyboard for the manual introduction of data corresponding to the postage to be printed and a Random Access Memory for real time operation. Data is stored in a Nonvolatile Memory upon power down and read into the Random Access Memory upon power up. U.S. Pat. No. 4,301,507 discloses an improvement in an electronic postage meter having two or more units that are each provided with computer control and describes a means for providing communication between units as well as with peripheral devices.
U.S. Pat. No. 4,481,604 describes, as an alternative memory system, a redundant memory system in which for each operation identical data is stored respectively in two identical CMOS battery-backed nonvolatile memories.
While the meters herein described each work well under normal conditions, there have been found to be significant numbers of times when operational anomalies have occurred. Even is such transient events occur only very irregularly, there are still chances that postal value may be lost or that other unknown conditions may cause malfunctions in the operation of the postage meter. In some cases it may be that under unanticipated circumstances the routines which are utilized for one task may have unintended consequences for other operations of the postage meter. When such anomalies occur, in these conventional postage meters the machine typically sets a fatal error which in turn requires the meter to be taken out of service. In addition to the obvious problem of meter down-time it has also been found in these meters that there may be no way to reconstruct the events that have occurred in order to recreate the circumstances of the malfunction or to determine if there was an undetected software error.
The conventional postage meters described in these patents normally continually cycle through various "idle" or other "housekeeping" routines while awaiting the occurrence of an event or request which will command the microcomputer program to perform a particular operation.
It has been found that many of the problems occurring in these meters may be alleviated or eliminated in a meter in accordance with the invention in which the status of the meter is monitored and the monitored data is used to schedule the tasks to be performed by the meter.
It is therefore an object of the invention described herein to provide a method and apparatus for monitoring the status of the meter to determine at each instant the condition of the meter with respect to inputs, outputs, meter switches and sensed internal conditions.
It is a second object of the invention to provide a meter operation in which each of the various tasks comprising the operation of the meter are independently actuable in a sequence or queue determined from monitoring the status of predetermined inputs, outputs, switches or sensed internal conditions.
It is a further object of the invention to provide the capability in an Electronic Postage Meter for the meter itself or for the passage of time to determine when a particular task should be scheduled for operation.